English

Noun

Pangenesis was Charles
Darwin's hypothetical mechanism for heredity. He presented this
'provisional hypothesis' in his 1868 work
The Variation of Animals and Plants Under Domestication and
felt that it brought 'together a multitude of facts which are at
present left disconnected by any efficient cause'. The etymology of
the word comes from the Greek
words pan (a prefix meaning "whole", "encompassing") and genesis
(birth) or genos (origin).

Pangenesis holds that body cells shed gemmules, which collect in the
reproductive organs prior to fertilization. Thus every cell in the
body has a 'vote' in the constitution of the offspring. Atavisms arise due
to the awaking of long-dormant gemmules, while limbs regenerate due
to the activation of gemmules from the missing limb.

Pangenesis itself is now seen as deeply flawed
and not supported by observation, yet it represents Darwin's
attempt to explain such diverse phenomena as:

Later Elaboration

In his later work, The
Descent of Man, Darwin elaborated further on the model. In a
section on the "Laws of inheritance," Darwin specified that two
elements in particular were most important: the transmission and
the development of inherited characteristics. Darwin's insights
were that characteristics could be transmitted which were not at
the time of transmission actually being manifest in the parent
organism, and that certain traits would manifest themselves at the
same point of development (say, old age) in both the parent and
child organisms. In order to make sense of his theory of sexual
selection, he also stipulated that certain traits could be
passed through organisms but would only develop depending on the
sex of the organism in question.

Galton's experiments on rabbits

Darwin's half-cousin
Francis
Galton conducted wide-ranging inquiries into heredity which led
him to refute Charles Darwin's hypothetical theory of pangenesis.
In consultation with Darwin, he set out to see if gemmules were transported in
the blood. In a long series of experiments in 1869 to 1871, he
transfused the blood between dissimilar breeds of rabbits, and
examined the features of their offspring http://www.abc.net.au/rn/science/ss/stories/s216074.htm.
He found no evidence of characters transmitted in the transfused
blood . Darwin challenged the validity of Galton's experiment,
giving his reasons in an article published in 'Nature'http://darwin-online.org.uk/content/frameset?itemID=F1751&viewtype=side&pageseq=1
where he wrote: "Now, in the chapter on Pangenesis in my "Variation
of Animals and Plants under Domestication," I have not said one
word about the blood, or about any fluid proper to any circulating
system. It is, indeed, obvious that the presence of gemmules in the
blood can form no necessary part of my hypothesis; for I refer in
illustration of it to the lowest animals, such as the Protozoa,
which do not possess blood or any vessels; and I refer to plants in
which the fluid, when present in the vessels, cannot be considered
as true blood." He goes on to admit: "Nevertheless, when I first
heard of Mr. Galton's experiments, I did not sufficiently reflect
on the subject, and saw not the difficulty of believing in the
presence of gemmules in the blood."

Historical precedents

In pangenesis one finds a remarkable
similarity to the work of
Pierre Louis Moreau de Maupertuis and
Georges-Louis Leclerc%2C Comte de Buffon, specifically their
use of the concept of "chemical affinity". A wider historical view
finds us analyzing the tension that Newton's concept, the "force of
gravity", created between himself and the contintental
materialists. The latter felt that this mysterious, invisible force
was akin to an invocation of mysticism. Likewise, the argument for
a "vis essentialis" in biology has a similar quasi-scientific sound
and might serve to remind us of the rudimentary state, and fertile
philosophical ground, of theoretical speculations during that
earlier period in time.

It is also a remarkable exercise, for the curious
student, to juxtapose the theory of pangenesis with modern concepts
in developmental biology and genetics, specifically, the origin,
migration, and function of the primordial germ cells and the
"chemical affinities" regarded in the study of DNA..

External links

Variation under Domestication, From: Freeman, R. B. 1977. The
Works of Charles Darwin: An Annotated Bibliographical Handlist. 2nd
edn. Dawson: Folkstone, at DarwinOnline, with links to online
versions of the 1st. edition, first and second issues, and the 2nd.
edition.